1. Field of the Invention
The present invention relates to an apparatus and a method for drying washed objects, and more specifically, to an apparatus and a method for drying washed objects being suitable for washing, rinsing, and drying substrates of semiconductor wafers.
2. Description of the Related Art
Heretofore, removal of moisture entered in trenches is an important factor in drying of miniaturized washed objects such as wafers after washing of precision substrates, and thus a drying apparatus using organic solvent vapor is employed. An apparatus shown in FIG. 1 is known as a drying apparatus using organic solvent vapor.
The drying apparatus 1 includes, as shown in FIG. 1, a drying tank 2 being box-shape having an opening on top thereof in cross section, a heating device (heater) 3 mounted on the bottom surface 2a of the drying tank 2, a cooling coil 4 provided on the upper part of the drying tank 2, a solvent trap 5 provided downwardly of the cooling coil 4, a wafer placing table 7 disposed in the drying tank 2 for placing a wafer 6 as a washed object thereon, and a solvent pooling section 8 disposed downwardly of the wafer placing table 7.
The drying apparatus 1 heats organic solvent 9 charged into the drying tank 2 to a boiling point by the heater 3 and generates organic solvent vapor in the upper portion thereof. A wafer 6 already washed and rinsed with water is then inserted and arranged in the vapor in the drying tank 2. Condensation of organic solvent occurs on the surface of the wafer 6 that is inserted and arranged in the drying tank 2, and then moisture attached on the surface of the wafer 6 is replaced by organic solvent which is more likely to evaporate, whereby the wafer 6 is progressively dried. The wafer 6 in the organic solvent vapor is gradually increased in temperature to an evaporating point (boiling point), and then is taken out of the mist atmosphere, where attached solvent component rapidly evaporates due to its low latent heat, to be completely dried.
The organic solvent heated and vaporized by the cooling coil 4 disposed on the upper part of the drying tank 2 is condensed and dropped in the solvent trap 5 for recovery and reusing. Likewise, solvent including moisture dropped from the wafer 6 is also recovered in the solvent pooling section 8.
The drying apparatus 1 in the related art demands attention to flames since organic solvent is heated by the heater 3, and consumes a lot of energy because it carries out heating and cooling. In addition, it requires a significant period of time until a vapor layer is formed by being heated by the heater 3, and consumes a large quantity of organic solvent due to evaporation. Further, when the washed objects come in contact with the mist layer, heat of vapor (gas phase) is absorbed by the washed object, thereby causing abrupt change in phase (gas phase to liquid phase) and reducing the vapor layer. Consequently, the washed object is exposed to the atmosphere, which may easily results in contamination, insufficient drying, and so on.